MailMover: escape mail folder name with double quotes

shlex.quote quoted with single quotes, which is not supported by
notmuch, so we have to quote and escape on our own

followup of afewmail#218 (comment)

afew/MailMover.py

@@ -5,7 +5,6 @@
 import notmuch
 import logging
 import os, shutil
-import shlex
 from subprocess import check_call, CalledProcessError
 
 from .Database import Database
@@ -23,7 +22,7 @@ class MailMover(Database):
     def __init__(self, max_age=0, rename = False, dry_run=False):
         super(MailMover, self).__init__()
         self.db = notmuch.Database(self.db_path)
-        self.query = 'folder:{folder} AND {subquery}'
+        self.query = 'folder:"{folder}" AND {subquery}'
         if max_age:
             days = timedelta(int(max_age))
             start = date.today() - days
@@ -55,7 +54,7 @@ def move(self, maildir, rules):
         for query in rules.keys():
             destination = '{}/{}/cur/'.format(self.db_path, rules[query])
             main_query = self.query.format(
-                folder=shlex.quote(maildir), subquery=query)
+                folder=maildir.replace("\"", "\\\""), subquery=query)
             logging.debug("query: {}".format(main_query))
             messages = notmuch.Query(self.db, main_query).search_messages()
             for message in messages: